Obesity is related to the rising incidence of type 2 diabetes and interventions leading to sustained weight loss are needed. Most weight loss trials have been implemented in academic centers under tightly controlled conditions with limited follow-up. The need for translation of successful interventions is clear. Since patients have regular contact with their primary care physicians (PCPs), an intervention that can be delivered through primary care practices could have better long-term outcomes. The Diabetes Prevention Program (DPP) is a model for a successful weight loss intervention, yet no programs to date have successfully adapted the DPP to a long-term primary care-based intervention. The study is a 5 year randomized controlled trial of 2 active treatment interventions based on the DPP model that will be delivered at primary care sites. The specific aims are to evaluate the effects of two interventions that are translations of the DPP Lifestyle Balance program, and are delivered through primary care practices, on the primary medical outcome of weight loss, secondary medical outcomes of blood pressure, fasting lipids and glycemia, and psychosocial outcomes of health behaviors and health-related quality of life. Secondary aims are to determine whether the DPP translation is more effective and/or cost effective delivered in a group format. Subjects will be recruited from 4 diverse primary care practices. There will be 2 active treatment groups, both based on the DPP Lifestyle Balance Program. All subjects will have contact with a primary care nurse and a behavioral weight loss coach. During the first year, in one group, the nurse will present the 12 DPP topics during phone calls (weekly for first 5 weeks, monthly thereafter) and the coach will make 3 phone contacts per month to promote adherence to behavioral weight loss strategies. In the second group, the nurse will facilitate group conference calls (weekly for first 5 weeks, monthly thereafter) to present the DPP material and foster peer support, and the coach will have 3 weekly phone contacts for the individualized aspects of the intervention. A second year of continued contact is included. The study is significant because a primary care based, telephone weight loss intervention will be able to reach more people, may be more effective, and could be easily adopted by primary care physicians, helping them help their patients lose weight successfully and maintain their weight loss. Interventions leading to sustained weight loss are needed to improve the public health and reverse the alarming rise in diabetes, its cardiovascular complications and other obesity-related illnesses. PUBLIC HEALTH RELEVANCE: Obesity is related to the rising incidence of type 2 diabetes and interventions leading to sustained weight loss are needed. The study is significant because a primary care based, telephone-delivered weight loss intervention will be able to reach more people, may be more effective, and could be easily adopted by primary care physicians, helping them help their patients lose weight successfully and maintain their weight loss. Interventions leading to sustained weight loss are needed to improve the public health and reverse the alarming rise in diabetes, its cardiovascular complications and other obesity-related illnesses.